A typical liquid crystal display apparatus includes a liquid crystal panel and a flat light source, which is provided on the rear surface of the liquid crystal panel. The flat light source includes the sidelight type and the direct-light type depending on how the light source is disposed.
A flat light source of the sidelight type (also called edge-light type) has its light sources disposed in a crystal liquid display near the side surface of the liquid crystal display apparatus, while a flat light source of the direct-light type has its light sources disposed to face the rear surface of the liquid crystal panel.
There is a sidelight type flat light source employing a light guide plate which receives light from the light sources and diffuses the light therein to supply uniform light to the rear surface of the liquid crystal panel.
In a flat light source employing such a light guide plate, light emitted from a sidelight part having line sources such as cold cathode fluorescent lamps (CCFL) or point light sources such as light emitting diodes (LED) is reflected in the light guide plate and diffused in a diffusion pattern made on the light guide plate, so that area light is obtained from the main surface of the light guide plate.
In this respect, Japanese Patent Application Laid-Open No. 2005-79038, for example, discloses a sidelight type flat light source employing point light sources such as LEDs each having its light emitting surface made in contact with the light incident surface of a light guide plate.
In the flat light source of such construction, light emitted from a light emitting region of each point light source effectively enters the light guide plate, which can avoid losses in incidence efficiency upon the light guide plate.
In contrast, when warpage occurs in the light guide plate, the light emitting region of each point light source is displaced from the light incident surface of the light guide plate, resulting in decreased incidence efficiency and degraded display quality.
Japanese Patent Application Laid-Open No. 2005-243533, for example, discloses preventing decrease in incidence efficiency due to warpage of the light guide plate by providing projections on the light guide plate to be engaged with an enclosure.
With such construction, however, problems of decreased incidence efficiency and degraded display quality still arise when the light emitting region of each point light source is displaced from the light incident surface of the light guide plate.
Further, the enclosure needs to have rigidity to compensate for warpage of the light guide plate, which causes problems of size increase of the liquid crystal display apparatus and construction difficulty. Furthermore, when engaging the light guide plate with the enclosure, they rub against each other to generate foreign matters, which results in display failure.